1. Field of the Invention
This invention concerns the use of sodium hydroxide to remove hydroperoxides from a lubricating oil.
2. Description of Related Art
Hydroperoxides are known to be a source of free radicals which cause oxidative degradation of hydrocarbon oils (see M. D. Johnson et al. SAE Paper No. 831684, November 1983). Hydroperoxides have also been shown to promote valve train wear in automotive engines (see SAE Paper Nos. 872156 and 872157 as well as J. J. Habeeb et al. "The Role of Hydroperoxides in Engine Wear and the Effect of Zinc Dialkyldithiophosphates", ASLE Transactions, Vol. 30, 4, p. 419-426). Furthermore, zinc dialkyldithiophosphate (ZDDP), which has been used as an antiwear agent in lubricating oils for several years, has also been found to decompose hydroperoxides (see ASLE Transactions, supra.). However, the ZDDP in the oil will become depleted such that the oil must be periodically replaced.
As such, in view of the deleterious effects resulting from the presence of hydroperoxides in lubricating oil, it would be desirable to have available a simple, yet convenient, method of decomposing hydroperoxides while extending the useful life of the oil before it must be replaced. One such method is described in U.S. Pat. No. 4,997,546 wherein hydroperoxides are contacted with a heterogenous hydroperoxide decomposer that is immobilized when contacting the oil so as not to pass into the oil. However, the method disclosed in U.S. Pat. No. 4,997,546 requires modification when the hydroperoxide decomposer is sodium hydroxide.